In the critical moments after the Nov. 20 shooting, the cops’ commanding officer and an emergency operator — responding to a 911 call from a neighbor and knowing the duo was in the area — tried to reach them in vain, sources said.

Akai Gurley, seen with 2-year-old daughter Akaila in center photo, was killed by rookie cop Peter Liang's bullet in the Nov. 20 shooting.

(Facebook)

“That’s showing negligence,” said a law enforcement source of the pair’s decision to text their union rep before making a radio call for help.

“The guy is dying and you still haven’t called it in?”

To make things even worse, the officers were uncertain of the exact address of the building in the Pink Houses they were in, according to their text messages, the sources said.

Blood is seen on the stairwell the day after the shooting. Sources say Liang texted his union representative instead of calling for help as Gurley lay dying.

(Alex Rud for new york daily news)

The explosive details of the immediate aftermath following the shooting of Gurley are at the center of an investigation by Brooklyn District Attorney Kenneth Thompson — who is poised to present evidence to a grand jury as early as the end of this month.

The two cops involved weren't supposed to be patrolling the Pink Houses' stairways that night, sources say.

(Theodore Parisienne for New York Daily News)

Adding to the tragedy surrounding Gurley’s death, the officers involved were not supposed to be doing a patrol in the stairways, the sources said.

Deputy Inspector Miguel Iglesias, then the head officer of the local housing command, ordered them not to carry out such patrols, known as verticals.

He opted instead for exterior policing in response to a spate of violence at the East New York housing project.

“They’ve done verticals before,” a police source said of the two officers.

“But Iglesias’ philosophy was, ‘I want a presence on the street, in the courtyards — and if they go into the buildings they were just supposed to check out the lobby.”

Another source said the commander was furious after the shooting, raging, “I told them not to do verticals.”

Brooklyn District Attorney Kenneth Thompson is investigating.

(Chase Guttman/New York Daily News)

Police Commissioner Bill Bratton characterized the incident as an “unfortunate tragedy” and an accident. Officials said Liang was holding a flashlight in his right hand and a Glock 9-mm. in the other when he opened the door to the eighth-floor landing.

One bullet flew out and apparently ricocheted into the chest of Gurley, who was on the seventh-floor landing and taking the stairs with his girlfriend Melissa Butler, 27.

The victim stumbled down to the fifth floor and Butler knocked on a woman’s door on the fourth floor, pleading for help. That woman called 911, a source said.

The building's superintendent had reportedly asked NYCHA to fix the lights months earlier.

(Theodore Parisienne for New York Daily News)

When Liang and Landau finally resurfaced on the radio, they reported an accidental discharge, added the source. Authorities have said they didn’t immediately know anyone was struck with the bullet.